Thread-gage.



F. O. WELLS & F. JUDGE.

THREAD GAGE.

APPLICATION FILED JAN. 24, 1913.

1,130 866 Patented Mar. 9, 1915.

REF- PLUG FOR 2 SCREW GAUGE arr WITNESSES: INVENTOR;

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FRANK o. WELLS AND FRANKLIN JUDGE, or

GREENFIELD, MASSACHUSETTS, ASSIGN- oRs T0 GREENFIELD TAP & DIE CORPORATION, or GREENEIELD, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS.

THREAD-GAGE.

The object of the invention is to provide a thread gage, which-is arranged to be correctly adjusted by comparison with a standard gage, whereby the size of screws may be accurately measured. 7

In. practice a single standard gage is used in a shop as a means for setting the thread gages given to the workman. This standard gage is one which has been measured by and certified to by the Bureau of Standards and is kept ordinarily in the oflice safe for use as a'reference gage. The thread gages given to theworkman for the measurement of screws, are frequently com pared with and set by this standard.

A preferred embodiment of my invention is shown for the purposes of illustration in the accompanying drawings in which:

Figure l is a side elevational view of the reference plug gage which has been standardized by some bureau organized for that purpose; Fig. 2 is an end elevational view of the thread gage, which is arranged to be.

set to the correct size by the reference plug shown in Fig. 1; Fig. 3 is a top plan view of Fig. 2 showing a flattened surface provided with suitable graduations whereby the size of screws may be measured; Fig. 4 is a sectional view taken on the line 55 of Fig. 2 which is drawn to an enlarged scale. In this view the root, pitch and outside diameter of the threads Of the reference plug shown in Fig. 1, are indicated by dotted lines. Furthermore, the slight taper in the opening of the adjustable gage is clearly indicated by the pair of dotted lines which are extended toshow the convergence therebetween.

Referring to the drawings in detail: a designates an adjustable thread gage which is given to the workman after having been correctly set from the reference plug Specification of Letters Patent.

I the gage.

Patented'Mar. 9, 1915.

Application filed January 24, 1913. Serial No. 743,884.

shown in Fig. 1. This gage is provided with two set screws opening d, which permits a slight spring action when the set screws 5 and c are operated. The upper surface of this gage a 1s flattened, as shown at e, and 7 indicates an opening in the upper portion of the ofthe surface 6 with the threaded hole of The reference plug, indicated generally by the reference letter 11,, is formed with a flattened surface/c. On a graduation m,.which indicates the pitch diameter of the reference plug-at that point. For the purposes ofillustration', theplug n and the gage a have been shown as designed for aone'half inch standard thread. The correct pitch diameter of a thread of this size is .4501 which numeral is indicated at thegraduation m in Fig. 1. The surface 6 of the gage a has a graduation marked .4501 and other graduations marked .00l-, .002 and .003. The latter are placed at intervals of two threads from the graduation .4501 and indicate a progressive reduction of diameter of the screw to be measured in a manner to be described.

Fig. 4. clearly shows by the converging dotted lines 9 the taper of the gage a. These; lines 9 are drawn through the roots of the thread on the gage a and the dimension f, between these lines, indicates the out.-

side diameter of the plug n. The pitch and i b and cand a narrow the latter is.

. gage, which results from the intersection I root diameters of theplug are indicated by the dimensions It and 2' respectively. The taper of the Opening in the gage a, as will be observed from Fig. 8 is at the rate of one one thousandth of an inch to a linear distance equal to two threads.

The gage a is first correctly set from the reference plug n. The plug 02. is screwed into the threaded opening of the gage until the tion .4501 on the gage a. The set screws 5 and c of the gage a are then adjusted so that there is an accurate fit between the reference plug and the threaded opening 1n thegage' After this adjustment has been made the plug n is removed from the gage and the latter is given to the workman for the measurement of screws.

The manner, in which screws are measured will now be described.- In practice, the measurement of a screw is taken on the graduation m registers with the gradua undersize.

sixth thread from the end. The pitch diameter at the sixth thread from the end must equal the correct pitch diameter .4501. Thus a screw of correct size, when threaded into 5 the opening of the gage a, would have its sixth thread opposite the graduation marked .4501. If the-sixth thread of the screw failed to reach this graduation, the screw is.

oversize and if it passes the graduationit is The amount of variation from the correct size is indicated by the graduations and might readily be determined without these graduations since two threads represent a variation of one one thousandth of an inch in pitch diameter. If when a screw is threaded into the opening of the gage a, the sixth thread thereof lies opposite the graduation marked .00l it is undersize in pitch diameter by one one thousandth of an inch. Similarly, the other graduations to the left of the mark .4501 indicate variations of two and three one thousandths of an inch below the required pitch diam eter. If the sixth thread fails to reach the mark A501 the amount of oversize may be estimated by counting the number of threads between the mark on the gage and the sixth thread from the-end of the screw, remembering that two threads represent one one thousandth of an inch in pitch diameter. Variations of less than one one thousandth of an inch may be easily determined by a skilled operator by. counting threads and half threads.

of an inch in pitch diameter. Obviously, the gage a also gives a check on the pitch of the screw, for if the screw and gage were of different pitch the former could not enter 40 the opening of the gage a any appreciable distance. Thus, I haveprovided a simple and accurate gage, by means of which a workman may measure screws in the manner Gapies o! thispatent may be obtained for It is thus very easy to determine 35 a deviation of one quarter of one thousandth described. This gage is arranged to be ad-I justed and set from a standard reference plug, whereby it is standardized. Gages have heretofore been used, which measure the size of a screw, but sofar as I am aware, no gage has been provided, which indicates the amount of variation in thediametera thereof.

WVhat we claim is:

1. A thread gage comprisingin combination, a body member formed with a tapered threaded opening therein, arranged to receive a screwto be measured, said body being: provided with a flattened upper portion having a graduation thereon to 1ndif-,

cate the correct size of said screw and other raduations toindicate deviations from said! correct size, said flattened upper portion;

intersecting the threaded opening, means to set the gage'from a standard reference plug,

all constructed and arranged ;so that thesize of the screw to be measured is indicated said opening.

2. A thread-gage formed with a tapered l threaded openingin the upper portionthere-e of, and an enlarged opening communicating therewith, the upper end of'the gage being flattened and intersecting said openingpsaid surface being prov1ded=w1th numerals des1g whereby when opening,

ing said first mentioned opening.

FRANK o. WELLS. FRANKLIN Witnesses-z CHARLES N. S'roDnARD, ROBERT O. MILLER- five cents each, by addressing the Commissioner of Patentl,

Washington, 10.10.

3 5 by the distance said screw: can be turned into 1 

